Tubulars are expanded for a variety of reasons. In the application a patch is expanded to repair cracked casing. In other applications tubulars or liners are expanded to connect to each other or to casing downhole to present a larger cross-sectional area for a segment of the well. In other applications, deformation or a collapse of casing from forces of the surrounding formation needs to be corrected to improve the borehole cross-sectional area in the affected zone.
Swages have been used to accomplish this task. Swages are generally a tapered shape coming to a fixed maximum diameter such that when pushed or pulled through the obstructed area results in making the tubular either resume its initial round dimension or expand the tubular into an even larger round dimension. More recently swages that could change circular dimension were disclosed by the inventors of the present invention in a U.S. provisional application filing on Feb. 11, 2002 having Ser. No. 60/356,061. That design allowed connected segments to move longitudinally with respect to each other to vary the circular maximum diameter of the swage. This ability had the advantage of changing size in the face of an obstruction to avoid sticking the swage or overloading the swage driving apparatus. This device had the capability of reducing to a smaller diameter to allow clearing of an obstruction. Its limitation was that if a tight spot adjacent the outside of only a part of the circumference of the tubular to be expanded was encountered, the swage reduced its diameter symmetrically to clear the obstruction. This resulted in a decrease in cross-sectional area beyond the amount necessary to clear the localized obstruction.
The present invention presents a compliant swage that has enough range of motion among its components to provide sufficient articulation to let the swage go out of round in profile. This permits a part of the swage to reduce in dimension at the localized obstruction while in the remaining regions where there is no such resistance, the expansion can continue as the swage advances. The net result is a larger cross-sectional area can be obtained than with the prior design and the obstruction can still be cleared. These and other advantages of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment and the claims, which appear below.